We don't do merges. It requires knowledge of all the languages.
Even if the messages are completely duplicate and were used for the exact same purpose? I could od it by hand, but I thought some admin tool for this is set up.
Could you at least abandon/invalid the merged message in order not to get new translations (as it is not used anywhere)?
If you think you have sufficient knowledge of all the affected languages, you can add (effectively new) translations by editing JSON files in the repository.